Liquid crystal display device

Abstract

An active matrix type liquid crystal display device comprises a liquid crystal layer using liquid crystal of a chiral smectic C phase or its sub-phase as a liquid crystal material, pixel electrodes provided on one side of the liquid crystal layer, a common electrode provided on the other side of the liquid crystal layer, switching elements for supplying a predetermined electric potential to the pixel electrodes, and at least two insulation layers, which are provided between the pixel electrode and the liquid crystal layer and between the common electrode and the liquid crystal layer and which include at least alignment films, a sum of values (d/ε) obtained by dividing a thickness d nm! of each insulation layer by a relative dielectric constant ε thereof at a frequency 1 kHz is set to be between 15 nm and 40 nm.

We claim: 
     
       1. A liquid crystal display device, comprising: a first substrate;   a plurality of scanning lines provided respectively for columns on the first substrate;   a plurality of signal lines provided respectively for rows on the first substrate;   a plurality of pixel electrodes on the first substrate, respectively, near points of intersections of the plurality of scanning lines and the plurality of signal lines;   a plurality of switching elements respectively inserted between the plurality of pixel electrodes and said plurality of signal lines, each of said plurality of switching elements comprising a conductive path and a control terminal for controlling said conductive path and conduction thereof, one end of said conductive path being connected to corresponding one of said plurality of pixel electrodes, the other end of said conductive path being connected to a corresponding one of said plurality of signal lines, the control terminal being connected to a corresponding one of said plurality of scanning lines;   a second substrate facing a surface of said first substrate on which said plurality of pixel electrodes are provided;   a common electrode provided on a surface of said second substrate, said surface opposing said first substrate;   a liquid crystal layer using liquid crystal of anyone of a chiral smectic C phase and a sub-phase thereof, and being inserted between said first and said second substrate; and   two or more insulation layers including an alignment film provided between said plurality of pixel electrodes and said liquid crystal layer and an alignment film layer provided between said common electrode and said liquid crystal layer,   wherein a sum of values (d/ε) obtained by dividing a thickness d  nm! of each of said two or more insulation layers by a relative dielectric constant ε of each of said layers at a frequency 1 kHz is set to be between 15 nm and 40 nm.   
     
     
       2. A liquid crystal display device according to claim 1, wherein said sum of values (d/ε) is set to be between 18 nm and 34 nm. 
     
     
       3. A liquid crystal display device according to claim 1, wherein liquid crystal used for said liquid crystal layer is anyone of deformed helix ferroelectric liquid crystal and thresholdless anti-ferroelectric liquid crystal. 
     
     
       4. A liquid crystal display device according to claim 1, wherein said liquid crystal display device has a function of allowing an image of one frame to be displayed when each of said plurality of signal lines supplies an image signal, said plurality of scanning lines supply scanning signals to sequentially drive said plurality of switching elements for respective columns and the driving of all of said plurality of scanning lines finish; and each of said plurality of signal lines has a function of supplying said image signal with a polarity inverted per a plurality of predetermined frames to a corresponding one of said plurality of pixel electrodes.   
     
     
       5. A liquid crystal display device according to claim 4, wherein said plurality of signal lines further has a function of supplying said image signal with a polarity alternately different per each of said plurality of signal lines. 
     
     
       6. A liquid crystal display device according to claim 5, wherein when said polarity of said image signal for arbitrary one of said plurality of signal lines is inverted, a corresponding one of said plurality of scanning lines supplies a pulse having a write-in time longer than a write-in time of the others of said scanning lines. 
     
     
       7. A liquid crystal display device according to claim 4, wherein said plurality of signal lines further have a function of supplying said image signal with a polarity alternately different per each of said plurality of signal lines and supplying said image signal with a polarity inverted per each of said plurality of scanning lines. 
     
     
       8. A liquid crystal display device according to claim 7, wherein when said polarity of said image signal for arbitrary one of said plurality of signal lines is inverted, a corresponding one of said plurality of scanning lines supplies a pulse having a write-in time longer than a write-in time of the others of said scanning lines. 
     
     
       9. A liquid crystal display device according to claim 4, wherein said polarity of said image signal of each of said plurality of signal lines is inverted in one or more of said scanning lines in each frame and said polarity of said image signal is the same in each of said scanning lines over a period of said plurality of predetermined frames. 
     
     
       10. A liquid crystal display device according to claim 9, wherein when said polarity of said image signal for arbitrary one of said plurality of signal lines is inverted, a corresponding one of said plurality of scanning lines supplies a pulse having a write-in time longer than a write-in time of the others of said scanning lines. 
     
     
       11. A liquid crystal display device according to claim 9, wherein the inversion of said polarity of said image signal for each of said plurality of signal lines is continuously carried out for first predetermined frames, said inversion of said polarity is suspended in succeeding second predetermined frames, which are repeated cyclically. 
     
     
       12. A liquid crystal display device according to claim 4, wherein said plurality of predetermined frames count 10 or more and 1000 or less.